由于 InvalidDefinitionException，javamoney 的 CurrencyUnit 不能用作字段的 class 并由 Jackson 反序列化

Question

I have a pojo that has a field of type CurrencyUnit from the javamoney library. When I marshall this pojo Jackson throws an exception. I remember this exception when I did not define any default constructor. But in this case I can not maintain the CurrencyUnit class since it's coming from a dependency. How can I still make this work?

Exception:

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `javax.money.CurrencyUnit` (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information\n at 

Answer 1

You should write a custom serialiser/deserialiser for each type from javax.money package you want to use or register already created module. For example: jackson-datatype-money .

You need to add dependency :

<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>jackson-datatype-money</artifactId>
    <version>1.1.1</version>
</dependency>

Simple example how to use:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import org.zalando.jackson.datatype.money.MoneyModule;

import javax.money.CurrencyUnit;
import javax.money.Monetary;

public class JsonMoneyApp {

    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);
        mapper.registerModule(new MoneyModule());

        CurrencyUnit cu = Monetary.getCurrency("USD");
        String json = mapper.writeValueAsString(cu);
        System.out.println(json);

        CurrencyUnit unit = mapper.readValue(json, CurrencyUnit.class);
        System.out.println(unit);
    }
}

above code prints:

"USD"
USD